The invention relates to heat treatable coated glass panes with a low-emissivity (low-e) and/or solar control coating. The invention also relates to methods of manufacturing said panes.
Heat treated glass panes which are toughened to impart safety properties and/or are bent are required for a large number of areas of application, for example for architectural or motor vehicle glazings. It is known that for thermally toughening and/or bending glass panes it is necessary to process the glass panes by a heat treatment at temperatures near or above the softening point of the glass used and then either to toughen them by rapid cooling or to bend them with the aid of bending means. The relevant temperature range for standard float glass of the soda lime silica type is typically about 580-690° C., the glass panes being kept in this temperature range for several minutes before initiating the actual toughening and/or bending process.
“Heat treatment”, “heat treated” and “heat treatable” in the following description and in the claims refer to thermal bending and/or toughening processes such as mentioned before and to other thermal processes during which a coated glass pane reaches temperatures in the range of about 580-690° C. for a period of several minutes, e.g., for up to about 10 minutes. A coated glass pane is deemed to be heat treatable if it survives a heat treatment without significant damage, typical damages caused by heat treatments being high haze values, pinholes or spots.
The inventors of the present invention have found that the parameter “haze” usually referred to when characterising the heat treatability of low-e and/or solar control coatings is often insufficient, as it does not fully reflect all types of defects that may arise during coating, heat treating, processing and/or handling of coated glass panes. Some of the known heat treatable coated glass panes show significant and clearly noticeable modifications of their optical properties and particularly of their reflection colour during a heat treatment.
It is desirable to be able to manufacture a range of coated products with a variety of light and/or heat transmission values in order to meet particular needs. One approach to address this objective is to use a common multilayer stack or platform for each of the different product types (e.g. low-e and solar control, and both toughenable and non-toughenable products) and then tune the optical properties of the stack by adding different thicknesses of an absorbing layer into each of the stacks.
In the context of the present invention, where a layer is said to be an “absorbing layer” this means that the layer has measurable absorption within the solar energy spectrum, including but not limited to the visible part of the spectrum.
Certain absorbing layers are known in the prior art. For instance, EP 0718250 A2 describes a coating stack with a protective metallic layer (e.g. Nb, Ta, Ti, Cr, Ni, NbTa, TaCr, or NiCr) located directly above a functional metallic layer such as silver. The thickness of the protective metallic layer may be modified to adjust the light transmission.
U.S. Pat. No. 4,816,054 A describes the coating of glass with single metal silicide functional layers (see claim 1) and specifically mentions the use of FeSi2, NiSi and NiSi2. No mention is made of other iron silicide layers or particular locations of metal silicide layers in multilayer stacks (the examples are all single coatings).
US 2005196632 A1 describes protective layers of, e.g., Zr silicide. Fe and Ni silicides are mentioned but no specific examples are given (see paragraph [0031]).